The invention relates to a method and to a device for identifying a damaged bearing of a rotating shaft.
In motors, in particular in electric motors, the bearings of a rotating motor shaft of the motor must frequently be monitored for bearing damage.
FIG. 1 illustrates a standard method and a standard device for identifying a damaged bearing of a rotating motor shaft of a motor. The motor as per FIG. 1 has two sides A and B, which are denoted in FIG. 1 by A and B. The motor comprises a motor shaft 1, which is mounted by means of two bearings 4a and 4b, and a housing 2. Rolling bearings, for example, can serve as bearings 4a and 4b. In order to measure the position, that is to say the angular position of the motor shaft in relation to an origin, and/or in order to measure the rotational speed of the motor shaft, the motor has a position sensor 3 which, in the example, is in the form of a resolver. The position sensor 3 outputs the position φ of the motor shaft, for the open-loop and/or closed-loop control of the motor, to an open-loop and/or closed-loop control unit of the motor. The motor does of course comprise further elements, but these are not illustrated in FIG. 1 as they are not essential to the understanding of the invention.
In the standard method for identifying a damaged bearing of a rotating motor shaft of a motor, a vibration sensor 11 is attached to the motor, which vibration sensor 11 measures the vibrations of the motor. The vibration sensor 11 passes a vibration signal S on to an external evaluating unit 13 which is not a constituent part of the open-loop and/or closed-loop control device. In the evaluating unit 13, an envelope is placed over the vibration signal S, the envelope undergoes a Fourier transformation and the absolute frequency response of the envelope is determined. If the absolute frequency response exceeds a limit value, bearing damage is identified and an alarm signal AL is generated. Here, the alarm signal AL is preferably generated after a relatively long period of exceedance of the limit value in order to avoid false alarms.
The standard method and the standard device for identifying a damaged bearing have some disadvantages. On the one hand, a vibration sensor must be provided, and on the other hand, the external evaluating unit 13 is usually required as a separate unit which is not a constituent part of an already-existing open-loop and/or closed-loop control device for the open-loop and/or closed-loop control of the motor. Said disadvantages make the above-described standard method and standard device for identifying a damaged bearing expensive and complex.